A. E. Feiring, Journal of Fluorine Chemistry, 13, 7-14 18 (1979) discloses the use of tantalum pentafluoride as a catalyst for the addition of hydrogen fluoride to tetra- and trichloroethene and related compounds. The catalyst is also useful for fluorine chlorine exchange reactions. However, under the conditions of the batch experiments, catalysts such as BF.sub.3, TaCl.sub.5, Ta.sub.2 O.sub.5, CoF.sub.3, V.sub.2 O.sub.5, ZrCl.sub.4, NbCl.sub.5, HgO, and WCl.sub.6 showed no catalytic activity at 150.degree. C. for the addition of HF to tetrachloroethene.
The use of tantalum pentafluoride as a catalyst for the addition of hydrogen fluoride to unsaturated compounds has been disclosed and claimed in U.S. Pat. No. 4,258,225.